The illusive gravity mech

[technohedge]

Hi Guys, I have a specific mechanism problem Im trying to solve. I cant divulge the specific application, however Im looking for examples of where this has been done in the past (or if this is even possible in peoples opinions).


I have a mechanism that employs a weighted pendulum type component that swings about a pivot. When the unit it attaches to is orientated vertically the pendulum swings into place and acts as a blocker for another lever.


When the unit is orientated horizontally the weight swings out of the way, allowing the lever to be moved. Its basically a gravity driven blocking mechanism.


The issue is that when the unit is orientated vertically and blocking the required lever,when the unit is moved around, (forwards or downwards) the weighted pendulum swings in the opposite direction as it pivots, thus removing the blocking function.


I have tried all sorts of slots and flats on the shaft that the weight pivots on to try and lock the weight when its in position, however it affects its ability to move out of that position when needed.


Has anyone witnessed such a mechanism working in industry? Or if its even possible?


Muchos gracias for any input

 

[LittleInch]

Some sort of drawing required here as it's very difficult to visualize what you are trying to do.

does sound to me like this isn't the best sort of blocking mechanism.

Remember - More details = better answers
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[handleman]

Gravity is acceleration.
You need to understand the "forward and upward" accelerations involved with this movement. If they are >9.81m/s^2 you won't be able to distinguish between a change in orientation and a movement that simulates it. This is a basic dynamics problem....

 

[MintJulep]

Sounds like you have discovered inertia!

 

[BUGGAR]

Without a picture, I'm imagining gyroscopic precession as a means to accomplish your mechanism.

 

[IRstuff]

Seems to me that one approach is to make it so that the pendulum needs to be ~90 degrees, say 80 degrees from its locking position to unlock the lever. This would therefore require essentially >5.7 g acceleration to swing the to the unlocked position, particularly if the pivot is damped.

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[technohedge]

littleinch: I cannot give a drawing sorry, its not an ideal situation but the mech sorta has to work like this...(if it can eventually work at all)

Handleman: it has to be able to handle pretty much any movement, hence the desire to disable the swing

Mintjulep: Yea, ive met her a few times before!

BUGGAR: Its a small and simple mech unfortunately, but i had some wikipedia fodder for work break today so thank you!

IR stuff: I thought about a dampened pivot, but shes a tiny and necessarily simple mech

Thanks guys!

 

[LittleInch]

Well if the pendulum swings out of the way due to the fact that the mysterious thing it is attached to moves horizontally, can't you set up some sort of lever blocking system?

How about a magnetic switch which operates when you're moving this thing around to hold the metal pendumum ball in? Or solenoid switch?

Why does it have to be a pendulum?

We can't do much without some sort of sketch here.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[MintJulep]

A "simple" mechanism that requires a lot of secondary clap-trap to work properly becomes not simple.

 

[handleman]

If it has to handle ANY motion, it is completely and entirely impossible according to the laws of physics. An object has no way of telling the difference between gravity and acceleration.

 

[chicopee]

I have made a few sketches based on the description of your OP and I realized that for the lever to operate as you described it should have a connecting mechanism to the "unit" which also incorporates the pendulum pivot point; also the unit can change position from horizontal to vertical and vice versa. Within that "unit" there will be a shock absorber to absorb the movement of the pendulum when the unit is vertical which will make the connecting mechanism release the lever to block the pendulum. The shock absorber must be free from the pendulum arm and securely anchored to the "unit". The pendulum arm must be properly designed so as to minimize bending. The motion of the pendulum can be made by anything in existence. This connecting mechanism between the "unit" and "lever" should also retract the lever when the unit is horizontally positioned thus allowing the pendulum a maximum swing.
What I am wondering about is what will make the "unit" change position from horizontal to vertical and vice versa?
See attached sketch of my understanding of your OP

 

[JStephen]

Use an overdamped pendulum with magnetic damping?